Pump control system



y 1962 R. H. COLE 3,032,993

PUMP CONTROL SYSTEM Filed Dec. 16, 1960 Z/S heetS-Sheet 1 RESERVOIRCHAMBER CONTROL l5 POWER PUMP PUMP 0 TO l4.7 PSI 0 TO 45 PSI OUTPUTCHAMBER INVENTOR. RICHARD H, COLE ATTORNEY y 2 R. H. COLE 3,032,993

PUMP CONTROL SYSTEM Filed Dec. 16, 1960 2 Sheets-Sheet 2 POWER PuMP 46 3L 5| I CONTROL PUMP 47 I4 AMPLIFIER 3 POSITION RELAY (MID POSITION) l ll -56 T RELAY \RELAY (DOWN POSITION) (UP POSITION) 7 INVENTOR.

RICHARD H. COLE ATTORNEY atent fifice 3,032,993 Patented May 8, 19623,032,993 PUMP CONTROL SYSTEM Richard H. Cole, Crystal, Minn, assignorto Minneapolis- Honeywell Regulator Company, Minneapoiis, Minn, acorporation of Delaware Filed Dec. 16, 1960, Ser. No. 76,281 7 Claims.(Cl. 60-52.)

' The present invention is directed to an arrangement of pumps wherein asmall control signal is all that is required to control a substantialpumping pressure. More specifically, the present invention is directedto a pair of electromagnetic conductive fluid pumps which are placed inseries opposition to one another so that the first pump, which is of alow pressure output, can control the fluid supplied to the second, orpower pump.

In the art of pumping various fluids, it becomes desirable in certaincases to be able to either modulate the flow of fluid in response to asignal, or to be able to completely cutoff the flow of fluid after aspecific volume has been pumped or delivered. In most conventionalpumping systems the modulation or control can be accomplished readily byinstalling control devices such as ordinary valves or by using variablecontrol pumps. The conventional approaches to control of pumped fluidsare not readily adapted to control of conductive fluids of the liquidmetal types. The various conductive fluids such as mercury, sodium,potassium, or a sodium-potassium mixture, are of corrosive and poisonousnatures and are quite diflicult to handle unless a hermetically sealedsystem is involved. In order to control a hermetically sealed system,ordinary valving becomes difficult due to the sealing problems and alsodue to the corrosive action of the conduction fluids on various membersof a valve that may be attempted for use.

In conductive fluids systems that utilize electromagnetic conductivefluid pumps of the Faraday type, there are no obstructions in thepumping channel which prevent reverse flow when the pump is deenergized.In order to hold a system using this type pump at a particular level,the electromagnetic conductive fluid pump either must be continuouslyenergized at a fixed level or some type of mechanical valving insertedto close the system upon deenergization of the pump. The presentinvention is directed to a unique control system that utilizes twoelectromagnetic conductive fluid pumps in series opposition. The firstpump, which is a low pressure pump, can be adapted to cut off the flowof fluid to a second or high pressure pump. With this arrangement it ispossible to utilize a very small control signal to in turn control apower pump capable of developing a rather high pressure. With thearrangement disclosed it is possible to either obtain olf-on control ora step modulated type control. The use of the present invention isparticularly adapted for modulation of an electromagnetic conductivefluid pump and actuator of the type disclosed in the United StatesPatent No. 2,948,118. This will be brought out more fully in thedescription of the present invention in the body of the specification.

It is thus the primary object of the present invention to disclose afluid control system utilizing two pumps in opposition so that the firstpump, with a low pressure output and low control signal, can handle thecontrol function in a system that utilizes a power pump developing ahigh pressure and utilizing a substantially greater amount of inputpower.

It is a further object of the present invention to disclose a fluidcontrol system for electromagnetic conductive fluid pumps that havenormally unobstructed, open passages therethrough.

It is yet a further object of the present invention to disclose a pumpcontrol system of a modulating type wherein the control power requiredis small compared to the power required to operate or modulate the mainfluid pump alone.

Still a further object of the present invention is to disclose a pumpcontrol system wherein an on-ofi type function can be accomplished witha relatively low power being used as the control signal as opposed tothe amount of power that would be required if an ordinary pump was used.

These and other objects will become apparent when the presentspecification is considered in its entirety along with the presenteddrawings.

In the present drawings,

FIGURE 1 is a schematic representation of an electromagnetic conductivefluid flow system utilizing a back to back arrangement of pumps in anelectromagnetic conductive fluid actuator;

FIGURE 2 is an isometric representation of a typical pump construction;

FIGURE 3 is an electrical schematic of a modulation control systemapplied to the pumps disclosed in FIG- UR-E 1;

FIGURE 4 is a partial representation of an alternate position of a relaydisclosed in FIGURE 3, and;

FIGURE 5 is another schematic representation of a third position for therelay disclosed in FIGURE 3.

The schematically represented system disclosed in FIG- URE 1 has avariable volume reservoir chamber 10 formed of any convenient fixedmaterial and is mounted on a base 11. The reservoir chamber 10 is sealedwith a bellows 12 that provides the variable volume feature. The bellows12 is exposed to a low pressure, in the present case disclosed as theatmosphere. The variable volume reservoir chamber is connected by pipe13 to a control pump 14 that is oriented to pump in the direction of thearrow, that is back into the reservoir chamber. An inlet of the controlpump 14 is connected to a pipe 15 to an inlet of power pump 16 which isoriented to pump in the indicated direction away from the control pump14. The output of the power pump 16 is supplied to a pipe 17 that is inturn connected to an output chamber 20 for output means generallyindicated at 19. The power or output chamber 20 is substantially thesame as the reservoir chamber 10 in that a fixed wall 21 is providedmounted on a base 22 and the chamber is sealed by a bellows 23. The endof the bellows 23 has a plate 24 attached thereto that in turn isconnected to an output shaft 25. A spring 26 is provided to bias theshaft 25 and plate 24 into the uppermost extended condition of thebellows 23. The shaft 25 further passes through an opening 27 in theplate 22 and is capable of moving upon any change in the content of theoutput chamber of the system.

The entire system described so far is filled with a fluid, preferably ofa conductive nature, so that the pumps 14 and 16 can be electromagneticconductive fluid pumps. The fluid fill normally would be mercury,potassium, sodium, or a mixture of sodium and potassium which iscommonly referred to as NaK. The overall system corresponds in manydetails to the electromagnetic pumpactuator device disclosed in Patent2,948,118 to Carlson et al. In the Carlson et al patent, the use of asingle electromagnetic conductive fluid pump and a pair of variablevolume chambers is shown as operating a valve which in the present casewould be attached to shaft 25. It is believed that the presentdescription and the information contained in the above referenced issuedpatent should clearly indicate the application or use of the presentsystem.

In order to better understand the system disclosed in FIGURE 1, atypical electromagnetic conductive fluid pump shown in FIGURE 2, will bedescribed. The

operation of the system in FIGURE 1 can then be more readily understood.A typical electromagnetic conductive fluid pump is formed having aC-shaped magnetic structure 30 which is wound with a coil of wire 31 tosupply a magnetic field across a gap 32 in the magnetic structure 30.The gap 32 is formed by two pole faces 33 and 34. It is obvious that thearrangement described will provide a magnetic field of substantialconcentration across the gap 32.

'A tube 35 of rectangular cross-section is fitted into gap 32 andsubstantially fills the gap. The tube 35, in a preferred embodiment,would be formed of a high resistance steel so as to be impervious to theconductive fluids that pass through it. The tube 35 has a pair ofelectrodes 36 and 37 attached to opposite walls thereof so that anelectric current can be passed through the tube and the conductive fluidthat passes through the tube in a direction mutually perpendicular tothe directional flow of the fluid and the magnetic field. It is obviousthat this construction provides a conventional electromagneticconductive fluid pump of the Faraday type and has absolutely noobstructions in the pumping channel. The entire pumping force developedin this type of a unit is due to the interaction of current flowingthrough the conductive fluid and reacting with a magnetic field. Sincethis type of unit is well known in the art, it is believed that nofurther detailed description of the unit is warranted. The supply ofcurrent to the electrodes 36 and 37, and the current to the coil 31, canbe from any convenient source either of alternating current or of directcurrent as long as the phase relationship between the current flow andthe magnetic field are properly maintained.

Once again considering the system in FIGURE 1, if the pumps 14 and 16are of the electromagnetic conductive fluid type disclosed in FIGURE 2,it becomes obvious that the passage connecting the reservoir chamber andthe output chamber is substantially a continuous open channel with noobstructions that would prevent reverse flow of fluid from the outputchamber to the reservoir upon the influence of spring 26 expanding thebellows 23 in an upward direction after the unit has once beencompressed by pumping pressure in the direction indicated for pump 16.Thus once pump 16 has been energized to supply a pumping pressure andhas compressed the bellows 23, some force must be maintained in thefluid system to retain the system in a stable or fixed state. Thisordinarily could be accomplished by the use of a valve, but due to thehighly corrosive nature of the electromagnetic conductive fluids used inthese systems, the valving is exceedingly difficult and has proved to beimpractical. In order to establish a fixed output position for theoutput chamber 2%, it has been discovered that a second pump, pump 14,can be inserted in the system as shown. By energizing the pump 14 in aback to back relationship with the pump 16, it is possible to cut offthe flow of fluid to the inlet of pump 16 by energizing the pump 14. Ifrepresentative values for the various pressures are considered, anexplanation of the operation is made much easier.

For example, if the atmospheric pressure of 14.7 pounds per square inchis applied to the reservoir chamber 10 and if pump 14 develops apressure equal to 14.7 pounds per square inch, it can prevent any fluidfrom being removed from the reservoir chamber 10. Pump 14, the controlpump, is capable of supplying from 0 to 14.7 pounds per square inch,with a relatively small amount of power input. This small amount ofpower input thus is capable of cutting off all fluid flow to pump 16, apower pump. The power pump is capable of developing any convenientpressure from 0 to as high as 300 pounds per square inch in somesystems. A normal system would utilize a pump which develops from O to45 pounds per square inch.

It thus become apparent that at any time it is desired to stop themovement of shaft by stopping the compression of bellows 23, it is onlynecessary to cut off the flow of fluid to pump 16 thereby stalling thepump and the output chamber. This can be accomplished at any time bysupplying 14.7 pounds per square inch at the inlet of the power pump inthe direction of the control pump 14. At any time it is desired to allowthe power pump to continue its operation the control pump is deenergizedallowing fluid to flow through it to the power pump thereby allowing anadditional supply of fluid to be pumped from the reservoir chamber 10into the output chamber 2'1).

With the system just described it is possible to supply a modulationsystem that is dependent only on a relatively small power input to thecontrol pump. While the total power required may be substantiallygreater, the amount of power required to control the device is quitesmall. Since electromagnetic conductive fluid pumps can be built usingstep down transformers an effective power pump can be readily built butthe power pump is quite ditficult to control due to the high currentsinvolved in the secondary circuits and the relatively high input powersto the unit as a whole. With the present arrangement it is possible tosupply a relatively small control Power to the control pump 14 andobtain a system that is effectively locked at any desired position ofshaft 25. In order to explain how this would be accomplished, a typicalcontrol circuit has been shown in FIGURE 3.

In the control circuit of FIGURE 3 a pair of conventional electricsupply lines 40 are shown with volts- 60 cycle power available. This canbe any convenient source but has been shown as a typical availablesource for convenience. A step down transformer 41 supplies a lowvoltage to a resistance bridge of the Wheatstone type. The Wheatstonebridge 42 has three legs which have fixed resistances and are 43, 44,and 45. A fourth leg 46 is a variable resistance which balances orunbalances the bridge 42. The variable resistance 46 could be atemperature sensitive resistance as would be used in a heating controlsystem and would be responsive to a localized ambient temperature. Theoutput of bridge 42 is supplied on conductors 47 and 48 to aconventional amplifier 50. The amplifier 50 is fed to a three positionrelay 51, which is shown in FIGURE 3 in its center position.

A second step down transformer 52 is provided which supplies power tothe power pump 16 and the control pump 14 by means of a common conductor53, and a conductor 54 that passes through contacts 55 and 56 of thethree position relay 51. In the position shown in FIGURE 3, the threeposition relay is supplying power to both the power pump 16 and thecontrol pump 14 at the same time. With this condition existing, inreferring back to FIGURE 1, the pump 14 and the pump 16 were bothenergized. With pump 14 energized and develop ing a pressure of 14.7pounds per square inch in the indicated direction, the pump 16 would bereceiving no further fluid flow from the reservoir chamber 10. At thesame time since pump 16 was not obtaining any fluid it would be able todo nothing further in the way of forcing the bellows 23 to compress andthe output shaft 25 would become stationary.

In FIGURE 4 there is shown the relay 51 with its input control conductor54 and contacts 55 and 56. The contact 55 is open while contact 56 isclosed. With this arrangernent the control pump would be energized butthe power pump would be deenergized. In this arrangement the spring 26would be expanding bellows 23 and forcing the conductive fluid from theoutput chamber 20 back into the reservoir chamber 10 with the aid of thepressure developed by the control pump 14. This allows the shaft 25 toreturn to its upper position.

In FIGURE 5 the relay 51 is disclosed with its input conductor 54 andthe contacts 55 and 56. In this case the relay is in its up position andthe contact 55 is closed withthe contact56 open. In this conditionthepower pump 16 would be energized but the control pump 14 would bedeenergized. This would allow the power pump to receive all the fluidthat it needs from the reservoir chamber in order to compress thebellows 2'3 and drive the shaft 25 in a downward direction. It becomesobvious that the various conditions of pumping are thus controlled bythe output by the amplifier 50 which is in turn controlled by thecondition of the variable resistance 46.

The pump control system that has been specifically de scribed in thepresent application is only one of many possible embodiments of thepresent invention. The specific control system disclosed represents onepractical approach that utilizes the invention and it is the intent ofthe present disclosure to show only one means of practicing the entireconcept. It is obvious that the back to back pump arrangement disclosedin FIGURE 1 could be utilized in various types of fluid systems forcontrol of various types of devices. The applicant therefore, Wishes tobe limited in the scope of this invention only by the appended claims.

I claim as my invention:

1. A control system for pump means: fluid reservoir means for supplyinga fluid and said reservoir means being exposed to a first pressure; pumpmeans connected to said reservoir means and oriented to pump said fluidinto said reservoir means; said pump means being capable of developing apressure equal to said first pressure; second pump means connected to aninlet of said first pump means and capable of developing a secondpressure from said inlet to an outlet of said second pump means; andsaid second pump means outlet connected to output means having avariable volume in order to transmit variations in volume to a device tobe operated; said first pump means controlling the flow of fluid to saidsecond pump means so as to block said second pump means from obtainingsaid fluid from said reservoir means thereby stalling the flow of fluidto or from said second pump means and stalling said output means.

2. A control system for fluid pumps having a pumping channel notconveniently obstructed to prevent reverse flow upon deenergization ofsaid pumps; a variable volume reservoir chamber for supplying a fluidand said chamber being exposed to a relatively low pressure; a pumpconnected to said reservoir chamber and oriented to pump said fluid intosaid chamber; said pump being capable of developing a pressure equal toor greater than said relatively low pressure; a second pump connected toan inlet of said first pump and capable of developing a high pressurefrom said inlet to an outlet of said second pump; and said second pumpoutlet connected to an output chamber having a variable volume in orderto transmit variations in volume to a device to be operated; said firstpump controlling the flow of fluid to said second pump so as to blocksaid second pump from obtaining said fluid from said reservoir chamberthereby stalling the flow of fluid to or from said second pump andstalling said output chamber.

3. A control system for electromagnetic conductive fluid pump meanshaving a continuously unobstructed pumping channel not convenientlyobstructed to prevent reverse flow upon deenergization of said pumpmeans; reservoir means for supplying a conductive fluid and saidreservoir means being exposed to a first pressure; electromagneticconductive fluid pump means connected to said reservoir means andoriented to pump said fluid into said reservoir means; said pump meansbeing capable of developing a pressure equal to said first pressure;second electromagnetic conductive fluid pump means connected to an inletof said first pump means and capable of developing a second pressurefrom said inlet to an outlet of said second pump means; and said secondpump outlet connected to an output means having a variable volume inorder to transmit variations in volume to a device to be operated; saidfirst pump means controlling the flow of fluid to said second pump meanssc as to block said second pump means from obtaining said fluid fromsaid reservoir means thereby stalling the flow of fluid to or from saidsecond pump means and stalling said output means.

4. A control system for electromagnetic conductive fluid pumps having acontinuously unobstructed pumping channel not conveniently obstructed toprevent reverse flow upon deenergization of said pumps; a conductivefluid reservoir chamber for supplying a conductive fluid; said chamberbeing variable in volume and being exposed to a relatively low pressure;an electromagnetic conductive fluid pump connected to said reservoirchamber and oriented to pump said fluid into said chamber; said pumpbeing capable of developing a pressure equal to or greater than saidrelatively low pressure; a second electromagnetic conductive fluid pumpconnected to an inlet of said first pump and capable of developing ahigh pressure from said inlet to an outlet of said second pump; and saidsecond pump outlet connected to an output chamber having a variablevolume in order to transmit variations in volume to a device to beoperated; said first pump controlling the flow of fluid to said secondpump so as to block said second pump from obtaining said fluid from saidreservoir chamber thereby stalling the flow of fluid to or from saidsecond pump and stalling said output chamber.

5. A control system for liquid metal pumps having a pumping channel notconveniently obstructed to prevent reverse flow upon deenergization ofsaid pumps; a reservoir chamber for supplying a liquid metal; saidchamber being variable in volume and being exposed to a relatively lowambient pressure, normally the atmosphere; a liquid metal pump connectedto said reservoir chamber and oriented to pump said liquid metal intosaid chamber; said pump being capable of developing a pressure equal toor greater than said relatively low pressure; a second liquid metal pumpconnected to an inlet of said first pump and capable of developing ahigh pressure from said inlet to an outlet of said second pump; and saidsecond pump outlet connected to an output chamber having a variablevolume in order to transmit variations in volume to a device to beoperated; said first pump controlling the flow of liquid metal to saidsecond pump so as to block said second pump from obtaining said liquidmetal from said reservoir chamber thereby stalling the flow of liquid toor from said second pump and stalling said output chamber.

6. A modulation system for pumps; condition respon sive means havingthree electrical output conditions; a variable volume reservoir chamberfor supplying a fluid and said chamber being exposed to a firstpressure; a pump connected to said reservoir chamber and oriented topump said fluid into said chamber upon either said first or said secondelectrical output conditions being connected to said pump; said pumpbeing capable of developing a pressure equal to said first pressure; asecond pump connected to an inlet of said first pump and capable ofdeveloping a high pressure from said inlet to an outlet of said secondpump upon either said second or said third electrical output conditionsbeing connected to said second pump; and said second pump outletconnected to an output chamber having a variable volume in order totransmit variations in volume to a device to be operated; said firstpump controlling the flow of fluid to said second pump in response tosaid condition responsive means.

7. A modulation system for electromagnetic conductive fluid pumps havinga continuously unobstructed pumping channel not conveniently obstructedto prevent reverse flow upon deenergization of said pumps; conditionresponsive means having three electrical output conditions; a conductivefluid reservoir chamber for supplying a conductive fluid; said chamberbeing variable in volume and being exposed to a low pressure; anelectromagnetic conductive fluid pump connected to said reservoirchamber and oriented to pump said fluid into said chamber upon eithersaid first or said second electrical output conditions being connectedto said pump; said pump being capable of developing a pressure equal tosaid low pressure; a second electromagnetic conductive fluid pumpconnected to an inlet of said first pump and capable of developing ahigh pressure from said inlet to an outlet of said second pump uponeither said second or said third electrical output conditions beingconnected to said second pump; and said second pump outlet connected toan output chamber having a variable volume in order to transmitvariations in volume to a device to be operated; said first pumpcontrolling the flow of fluid to said second pump so as to block saidsecond pump from obtaining said fluid from said reservoir chamberthereby stalling the flow of fluid to or from said second pump andstalling said output chamher in response to said condition responsivemeans second electrical output condition.

No references cited.

